feat: Jump highlight customizations

Closes #27

- Highlight group 'OutlineJumpHighlight' (links to Visual by default)
- Config: outline_window.jump_highlight_duration (integer for
  milliseconds, or boolean to enable/disable)

README.md

@@ -46,6 +46,7 @@ Table of contents
 * [Highlights](#highlights)
   * [Outline window](#outline-window)
   * [Preview window](#preview-window)
+  * [Other highlight groups](#other-highlight-groups)
 * [Lua API](#lua-api)
 * [Tips](#tips)
 * [Recipes](#recipes)
@@ -177,6 +178,9 @@ Pass a table to the setup call with your configuration options.
     auto_close = false,
     -- Automatically scroll to the location in code when navigating outline window.
     auto_jump = false,
+    -- boolean or integer for milliseconds duration to apply a temporary highlight
+    -- when jumping. false to disable.
+    jump_highlight_duration = 300,
 
     -- Vim options for the outline window
     show_numbers = false,
@@ -526,7 +530,7 @@ outline_window = {
 },
 ```
 
-Possible highlight groups provided by outline.nvim to customize:
+Possible highlight groups for the outline window:
 
 | Highlight            | Description                                          |
 | -------------------- | ---------------------------------------------------- |
@@ -550,6 +554,15 @@ preview_window = {
 },
 ```
 
+### Other highlight groups
+
+| Highlight            | Description                                                |
+| -------------------- | ---------------------------------------------------------- |
+| OutlineJumpHighlight | Used for indicating cursor position when jumping/focusing  |
+
+You can also use `outline_window.jump_highlight_duration` to customize in milliseconds,
+how long the highlight is applied for.
+
 ## Lua API
 
 Outline.nvim provides the following public API for use in lua.

lua/outline/config.lua

@@ -32,6 +32,7 @@ M.defaults = {
     show_cursorline = true,
     hide_cursor = false,
     winhl = "OutlineDetails:Comment,OutlineLineno:LineNr",
+    jump_highlight_duration = 500,
   },
   preview_window = {
     auto_preview = false,

lua/outline/init.lua

@@ -105,7 +105,17 @@ function M.__goto_location(change_focus)
     M.state.code_win,
     { node.line + 1, node.character }
   )
-  utils.flash_highlight(M.state.code_win, node.line + 1, true)
+
+  if vim.fn.hlexists('OutlineJumpHighlight') == 0 then
+    vim.api.nvim_set_hl(0, 'OutlineJumpHighlight', { link = 'Visual' })
+  end
+  utils.flash_highlight(
+    M.state.code_win,
+    node.line + 1,
+    cfg.o.outline_window.jump_highlight_duration,
+    'OutlineJumpHighlight'
+  )
+
   if change_focus then
     vim.fn.win_gotoid(M.state.code_win)
   end

lua/outline/utils/init.lua

@@ -111,9 +111,12 @@ function M.merge_items_rec(new_node, old_node, index, parent)
 end
 
 function M.flash_highlight(winnr, lnum, durationMs, hl_group)
+  if durationMs == false then
+    return
+  end
   hl_group = hl_group or "Visual"
   if durationMs == true or durationMs == 1 then
-    durationMs = 300
+    durationMs = 500
   end
   local bufnr = vim.api.nvim_win_get_buf(winnr)
   local ns = vim.api.nvim_buf_add_highlight(bufnr, 0, hl_group, lnum - 1, 0, -1)